DERIVATIVE INSTRUMENTS 3 (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets/liabilities	$ 76,562		$ 82,778
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	76,562		82,778
Gross amounts not offset in the balance sheet, Financial Instruments	(39,526)	[1]	(28,082)	[1]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	0		(498)
Net amount	37,036		54,198
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(110,166)		(100,124)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(110,166)		(100,124)
Gross amounts not offset in the balance sheet, Financial Instruments	39,526	[2]	28,082	[2]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	17,275		29,639
Net amount	(53,365)		(42,403)
Interest Rate Contract [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(7,890)		(6,676)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(7,890)		(6,676)
Gross amounts not offset in the balance sheet, Financial Instruments	0		0
Gross amounts not offset in the balance sheet, Cash Collateral Posted	0		0
Net amount	$ (7,890)		$ (6,676)

[1] The balances at March 31, 2014 and December 31, 2013 were related to derivative liabilities which can be net settled against derivative assets.

[2] The balances at March 31, 2014 and December 31, 2013 were related to derivative assets which can be net settled against derivative liabilities.